NODRAMA - For a man with that handle you certainly like to make a "Drama" out of other peoples honest statements.

Sorry but I'm with NODRAMA. Posting a pic of the 365 system, which is about as different as you can get from the 169 and labelling the duplex bearing as item16 is not helpful at all.

Looking at your 365 diagram, number 21 is about the closest you could get to where the duplex bearing is.The duplex bearing is outboard of the tailrotor and is nowhere near the hydraulic part of the servo.

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For those that can read English.

Quote:

Ignore the fact that this is actually a 365 but the principal is near enough -

Where it is physically is irrelevant - it performs that same function.

The issue that is in the debate is the consequences of a failure of the duplex bearing.

Thanks for the pics nodrama.

As you seem to be conversant with the type can you inform us as to how the pitch change shaft is locked against rotation at the servo end apart from the clamp up and a split pin and a bit of lockwire .

Because this forum is for armchair speculation/discussion. Whether or not it's all pointless is a matter of opinion... As for, "I told you so"...here's my theory. Somehow the aircraft was released from the factory in 2016 with an 'incorrect installation of the TR servo-actuator'. In practice, probably meaning that the cotter pin and lock-wire were never fitted, allowing the nut to work its way loose over time until the final (as it turned out) pedal input allowed it to fall off, resulting in complete loss of tail rotor control. This is entirely pointless (but, I believe, harmless) speculation from my armchair based, almost entirely, on the preceding 42 pages of discussion.

If you look at p11,#216,pic of tail rotor,it appears that the t/r `spider is intact,and appears to have a `device` on the outside of the `spider`...perhaps `nodrama` can comment if this appears normal..? nut /bolt still attached...?

In my opinion, all that one can tell from that photo is that there has been a catastrophic, and very sad, helicopter crash. That's what the AAIB are for. That 'device' is nothing more than a cover, or cap, for where the duplex bearing is housed.

How robust is this spider and duplex bearing? separate component or integral with the TGB? what's its overhaul life and inspection schedule? greased bearing or oil supplied from TGB? c'mon nodrama, if you're experienced, share and educate.

The nice thing, with a tail rotor failure in hoover or low speed is that you DIRECTLY and FIRST OF ALL goes for an autorotation by lowering the collective all the way to the lower stop. You don’t need to think if a cotter pin, a nut or all the tail rotor blades are missing. You -bang!- go for autorotation. If this accident was a tail rotor drive failure you had to land immediately, even if in trees, but here you had a few options like open areas where you probably could make a survivable ”landing".

Look at tailrotor failures like this: If you hesitate to go in autorotation you are toasted, but if you go in to a autorotation and it shows wrong, you can always change your mind. To survive a helicopter, always think negative for a positive outcome.

The different types of tail rotor failures and necessary actions taken are well known and are described in all helicopter manuals

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Arizona, your answer is too simplistic and unfortunately doesn't take into account that not all tail rotor malfunctions involve a loss of drive/thrust. In the situation where the tail rotor continues to be driven but pitch control is lost and the tail rotor goes to maximum positive pitch, entering auto-rotation might be the last control input you ever made.

Shy, I am reminded of an old aphorism (maybe from Einstein) that a great many complex problems have simple, clear, and wrong answers. (ref to what you responded to) I'm with you; an incorrect response to a particular malfunction can make things worser faster.

Crab, simply as a matter of interest and as I have easy access to a Level D 139 FFS, I had a go yesterday at using the technique discussed by you and DB. Even in the sim, and I knew it was coming, I very quickly became disorientated. I even found it difficult to take my hand off the collective to kill the engine mode switches. I felt I had no control whatsoever of the helicopter and was just along for the ride. No real thanks to me, the sim helicopter did remain level and I eventually put the collective down quickly. I got away with a successful level, spinning landing but I was very surprised at how quickly I lost all references. I carried out this exercise from 20 ft. From 400 feet I have absolutely no doubt it would be impossible. IMHO and as we seem to all agree, those poor guys didn't stand a chance.

Crab, simply as a matter of interest and as I have easy access to a Level D 139 FFS, I had a go yesterday at using the technique discussed by you and DB. Even in the sim, and I knew it was coming, I very quickly became disorientated. I even found it difficult to take my hand off the collective to kill the engine mode switches. I felt I had no control whatsoever of the helicopter and was just along for the ride. No real thanks to me, the sim helicopter did remain level and I eventually put the collective down quickly. I got away with a successful level, spinning landing but I was very surprised at how quickly I lost all references. I carried out this exercise from 20 ft. From 400 feet I have absolutely no doubt it would be impossible. IMHO and as we seem to all agree, those poor guys didn't stand a chance.

Hi-Hover, take a look at the Cardiff Police TR Malfunction. In the report the Commander stated he got totally confused by the image outside the windscreen so he settled on looking out the side window. This seemed to provide enough references for him to lower the collective, power on, and accept a trade of between ROD and yaw rate. He states that as he saw the surface appearing he pulled the collective all the way up to cushion the impact. Power on throughout. However, I am not sure if the references in any SIM would facilitate this or indeed of the flight loop allows for a reasonable attempt. Different type (355) also.

Sure, I agree, simulation has limitations, it was a different type from your student, and not even a 169. My point is simply that, after 40 years and 14,000 hours in the game, and being ready for the exercise, and having been in a helicopter with a tail rotor failure, I found it quite impossible to accept the rate of yaw with any form of control. I would need much more spare capacity.